Merge bitcoin#29233: build: depends move macOS C(XX) FLAGS out of C & CXX

cbc9bf1 build: move -mlinker-version to *FLAGS (fanquake)
42b2283 depends: deduplicate use of mmacosx-version-min in macOS build (fanquake)

Pull request description:

  Move some C/CXX FLAGS out of C/CXX. The remaining flags are host/SDK related, and will need some more thought.
  This is more correct in any case, and simplifies future changes.
  Related to bitcoin#21778.

ACKs for top commit:
  theuni:
    utACK cbc9bf1
  TheCharlatan:
    ACK cbc9bf1

Tree-SHA512: 373216c1de32375faddc161ecc09b14fed0e0994cbd5ed62c862c38a5aea80c7f1740f32f36b8a60ac1caf749309750d22164c50b89916f41838d6453296ac4a

Author: fanquake

depends/builders/darwin.mk

@@ -11,8 +11,8 @@ build_darwin_SHA256SUM=shasum -a 256
 build_darwin_DOWNLOAD=curl --location --fail --connect-timeout $(DOWNLOAD_CONNECT_TIMEOUT) --retry $(DOWNLOAD_RETRIES) -o
 
 #darwin host on darwin builder. overrides darwin host preferences.
-darwin_CC=$(shell xcrun -f clang) -mmacosx-version-min=$(OSX_MIN_VERSION) -isysroot$(shell xcrun --show-sdk-path)
-darwin_CXX:=$(shell xcrun -f clang++) -mmacosx-version-min=$(OSX_MIN_VERSION) -stdlib=libc++ -isysroot$(shell xcrun --show-sdk-path)
+darwin_CC=$(shell xcrun -f clang) -isysroot$(shell xcrun --show-sdk-path)
+darwin_CXX:=$(shell xcrun -f clang++) -stdlib=libc++ -isysroot$(shell xcrun --show-sdk-path)
 darwin_AR:=$(shell xcrun -f ar)
 darwin_RANLIB:=$(shell xcrun -f ranlib)
 darwin_STRIP:=$(shell xcrun -f strip)

depends/hosts/darwin.mk

@@ -79,24 +79,29 @@ $(foreach TOOL,$(cctools_TOOLS),$(eval darwin_$(TOOL) = $$(build_prefix)/bin/$$(
 darwin_CC=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH \
               -u OBJC_INCLUDE_PATH -u OBJCPLUS_INCLUDE_PATH -u CPATH \
               -u LIBRARY_PATH \
-            $(clang_prog) --target=$(host) -mmacosx-version-min=$(OSX_MIN_VERSION) \
-              -B$(build_prefix)/bin -mlinker-version=$(LD64_VERSION) \
+              $(clang_prog) --target=$(host) \
+              -B$(build_prefix)/bin \
               -isysroot$(OSX_SDK) -nostdlibinc \
               -iwithsysroot/usr/include -iframeworkwithsysroot/System/Library/Frameworks
 
 darwin_CXX=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH \
                -u OBJC_INCLUDE_PATH -u OBJCPLUS_INCLUDE_PATH -u CPATH \
                -u LIBRARY_PATH \
-             $(clangxx_prog) --target=$(host) -mmacosx-version-min=$(OSX_MIN_VERSION) \
-               -B$(build_prefix)/bin -mlinker-version=$(LD64_VERSION) \
+               $(clangxx_prog) --target=$(host) \
+               -B$(build_prefix)/bin \
                -isysroot$(OSX_SDK) -nostdlibinc \
                -iwithsysroot/usr/include/c++/v1 \
                -iwithsysroot/usr/include -iframeworkwithsysroot/System/Library/Frameworks
 
-darwin_CFLAGS=-pipe -std=$(C_STANDARD)
-darwin_CXXFLAGS=-pipe -std=$(CXX_STANDARD)
+darwin_CFLAGS=-pipe -std=$(C_STANDARD) -mmacosx-version-min=$(OSX_MIN_VERSION)
+darwin_CXXFLAGS=-pipe -std=$(CXX_STANDARD) -mmacosx-version-min=$(OSX_MIN_VERSION)
 darwin_LDFLAGS=-Wl,-platform_version,macos,$(OSX_MIN_VERSION),$(OSX_SDK_VERSION)
 
+ifneq ($(build_os),darwin)
+darwin_CFLAGS += -mlinker-version=$(LD64_VERSION)
+darwin_CXXFLAGS += -mlinker-version=$(LD64_VERSION)
+endif
+
 darwin_release_CFLAGS=-O2
 darwin_release_CXXFLAGS=$(darwin_release_CFLAGS)